Adipose-Derived Stem Cells in a Resilient In Situ Forming Hydrogel Modulate Macrophage Phenotype

Effects of nanographene oxide on adipose-derived stem cell cryopreservation

Cryoinjury mitigation is key in cell cryopreservation. Here, we aimed to assess the effectiveness of nanographene oxide (nano-GO) for improving cryoprotectant agents (CPAs) in human adipose stem cell (hADSC) cryopreservation. For in vitro experiments, nano-GO (5 μg/mL) was added to the CPAs in the control, and passage (P) 2 hADSCs were collected and cryopreserved for around two weeks. We compared cytotoxicity, cell viability, immunophenotypes, proliferation, cell apoptosis, and tri-lineage differentiation. In vivo, studies used lipoaspirate to create non-enriched or hADSC-enriched fat tissues by combining it with PBS or hADSCs cryopreserved with the aforementioned CPAs. Each nude mouse received a 0.3 mL subcutaneous injection of the graft. At 12 weeks, the grafts were harvested. Histology, adipocyte-associated genes and protein, vascular density and angiogenic cytokines, macrophage infiltration, and inflammatory cytokines were analyzed. Nano-GO CPA contributed to increased cell viability, improved cell recovery, and lowered levels of early apoptosis. Nano GO at concentrations of 0.01-100 μg/mL caused no cytotoxicity to hADSCs. The absence of nano GOs in the intracellular compartments of the cells was confirmed by transmission electron microscopy. The fat grafts from the CPA-GO group showed more viable adipocytes and significantly increased angiogenesis compared to the PBS and CPA-C groups. Adding hADSCs from the CPA-GO group to the graft reduced macrophage infiltration and MCP-1 expression. Nano-GO plays an anti-apoptotic role in the cryopreservation of hADSCs, which could improve the survival of transplanted fat tissues, possibly via improved angiogenesis and lower inflammatory response in the transplanted adipose tissue.

Adipose-derived stem cells in immune-related skin disease: a review of current research and underlying mechanisms

Adipose-derived stem cells (ASCs) are a critical adult stem cell subpopulation and are widely utilized in the fields of regenerative medicine and stem cell research due to their abundance, ease of harvest, and low immunogenicity. ASCs, which are homologous with skin by nature, can treat immune-related skin diseases by promoting skin regeneration and conferring immunosuppressive effects, with the latter being the most important therapeutic mechanism. ASCs regulate the immune response by direct cell-cell communication with immune cells, such as T cells, macrophages, and B cells. In addition to cell-cell interactions, ASCs modulate the immune response indirectly by secreting cytokines, interleukins, growth factors, and extracellular vesicles. The immunomodulatory effects of ASCs have been exploited to treat many immune-related skin diseases with good therapeutic outcomes. This article reviews the mechanisms underlying the immunomodulatory effects of ASCs, as well as progress in research on immune-related skin diseases.

Rapamycin antagonizes angiogenesis and lymphangiogenesis through myeloid-derived suppressor cells in corneal transplantation

Rapamycin is an immunosuppressive drug that is widely used in the postsurgery management of transplantation. To date, the mechanism by which rapamycin reduces posttransplant neovascularization has not been fully understood. Given the original avascularity and immune privilege of the cornea, corneal transplantation is considered as an ideal model to investigate neovascularization and its effects on allograft rejection. Previously, we found that myeloid-derived suppressor cells (MDSC) prolong corneal allograft survival through suppression of angiogenesis and lymphangiogenesis. Here, we show that depletion of MDSC abolished rapamycin-mediated suppression of neovascularization and elongation of corneal allograft survival. RNA-sequencing analysis revealed that rapamycin dramatically enhanced the expression of arginase 1 (Arg1). Furthermore, an Arg1 inhibitor also completely abolished the rapamycin-mediated beneficial effects after corneal transplantation. Taken together, these findings indicate that MDSC and elevated Arg1 activity are essential for the immunosuppressive and antiangiogenic functions of rapamycin.

Interstitial Injection of Hydrogels with High-Mechanical Conductivity Relieves Muscle Atrophy Induced by Nerve Injury

Injectable hydrogels have been extensively used in tissue engineering where high mechanical properties are key for their functionality at sites of high physiological stress. In this study, an injectable, conductive hydrogel is developed exhibiting remarkable mechanical strength that can withstand a pressure of 500 kPa (85% deformation rate) and display good fatigue resistance, electrical conductivity, and tissue adhesion. A stable covalent cross-linked network with a slip-ring structure by threading amino β-cyclodextrin is formed onto the chain of a four-armed (polyethylene glycol) amino group, and then reacted with the four-armed (polyethylene glycol) maleimide under physiological conditions. The addition of silver nanowires enhances the hydrogel's electrical conductivity, enabling it to act as a good conductor in vivo. The hydrogel is injected into the fascial space, and the results show that the weight and muscle tone of the atrophied gastrocnemius muscle improve, subsequently alleviating muscle atrophy. Overall, this study provides a simple method for the preparation of a conductive hydrogel with high mechanical properties. In addition, the interstitial injection provides a strategy for the use of hydrogels in vivo.

Macrophage Polarization in Response to Biomaterials for Vascularization

Vascularization of tissue engineering constructs is an urgent need for delivering oxygen and nutrients and promoting tissue remodeling. As we all know, almost all implanted biomaterials elicit immune responses. Interestingly, the immunomodulatory biomaterials can utilize the inherent regenerative capability of endogenous cells and stem cells recruited by the activated immune cells to facilitate anagenesis and tissue remodeling. Macrophages, as almost ones of the first responses upon the implantation of biomaterials, play a vital role in guiding vascular formation and tissue remodeling. The polarization of macrophages can be influenced by the physical and chemical properties of biomaterials and thus they display diverse function states. Here, this review focus on the macrophage polarization in response to biomaterials and the interactions between them. It also summarizes the current strategies to promote vascularization of tissue engineering constructs through macrophage responses.

Strategies to Overcome the Barrier of Ischemic Microenvironment in Cell Therapy of Cardiovascular Disease

The transplantation of various immune cell types are promising approaches for the treatment of ischemic cardiovascular disease including myocardial infarction (MI) and peripheral arterial disease (PAD). Major limitation of these so-called Advanced Therapy Medicinal Products (ATMPs) is the ischemic microenvironment affecting cell homeostasis and limiting the demanded effect of the transplanted cell products. Accordingly, different clinical and experimental strategies have been evolved to overcome these obstacles. Here, we give a short review of the different experimental and clinical strategies to solve these issues due to ischemic cardiovascular disease.

Ad-Dressing Stem Cells: Hydrogels for Encapsulation

Regenerative medicine is a novel scientific field that employs the use of stem cells as cell-based therapy for the regeneration and functional restoration of damaged tissues and organs. Stem cells bear characteristics such as the capacity for self-renewal and differentiation towards specific lineages and, therefore, serve as a backup reservoir in case of tissue injuries. Therapeutically, they can be autologously or allogeneically transplanted for tissue regeneration; however, allogeneic stem cell transplantation can provoke host immune responses leading to a host-versus-transplant reaction. A probable solution to this problem is stem cell encapsulation, a technique that utilizes various biomaterials for the creation of a semi-permeable membrane that encases the stem cells. Stem cell encapsulation can be accomplished by employing a great variety of natural and/or synthetic hydrogels and offers many benefits in regenerative medicine, including protection from the host’s immune system and mechanical stress, improved cell viability, proliferation and differentiation, cryopreservation and controlled and continuous delivery of the stem-cell-secreted therapeutic agents. Here, in this review, we report and discuss almost all natural and synthetic hydrogels used in stem cell encapsulation, along with the benefits that these materials, alone or in combination, could offer to cell therapy through functional cell encapsulation.

Injectable Hyaluronic Acid Hydrogel Loaded with Functionalized Human Mesenchymal Stem Cell Aggregates for Repairing Infarcted Myocardium

Conventional strategies of stem cell injection in treating myocardial infarction (MI) remain a challenge because of low retention rate and insufficient secretion of exogenous cytokines for efficiently improving the microenvironment in the infarcted myocardium, thus hampering the therapeutic effect. Herein, poly(lactic-co-glycolic acid) (PLGA) microparticles modified with human VE-cad-Fc fusion protein are fabricated and integrated with human mesenchymal stem cells (hMSCs) to construct functionalized MSC aggregates (FMAs). This fusion protein can effectively promote the paracrine activity of MSCs. The FMA is encapsulated with an injectable hyaluronic acid (HA)-based hydrogel, which is prepared by Schiff base reaction between oxidized HA (OHA) and hydrazided HA (HHA). The OHA@HHA hydrogel loading FMA is injected into the infarcted myocardium of rats, thereby efficiently improving the MI microenvironment in terms of decreased expressions of inflammatory cytokines and upregulated secretion of angiogenic factors compared to the plain hydrogel only and hydrogel encapsulating MSCs. The results of both echocardiography and histological analyses demonstrate the efficient reconstruction of cardiac function and structure and revascularization in the infarct myocardium. The delivery of functionalized stem cell aggregates with an injectable hydrogel offers a promising strategy for treating myocardial infarction and may be expanded to other tissue repair and reconstruction.

Monounsaturated Fatty Acids in a High-Fat Diet and Niacin Protect from White Fat Dysfunction in the Metabolic Syndrome

SCOPE

Obesity is a principal causative factor of metabolic syndrome. Niacin potently regulates lipid metabolism. Replacement of saturated fatty acids by MUFAs or inclusion of omega-3 long-chain PUFAs in the diet improves plasma lipid levels. However, the potential benefits of niacin in combination with MUFAs or omega-3 long-chain PUFAs against white adipose tissue (WAT) dysfunction in the high fat diet (HFD)-induced metabolic syndrome are unknown.

METHODS AND RESULTS

Male Lep^ob/ob LDLR^-/- mice are fed a chow diet or HFDs based on milk cream (21% kcal), olive oil (21% kcal), or olive oil (20% kcal) plus 1% kcal from eicosapentaenoic and docosahexaenoic acids, including immediate-release niacin (1% w/v) in drinking water, for 8 weeks. Mice are then phenotyped. Dietary MUFAs are identified as positive regulators of adipose NAD⁺ signaling pathways by triggering NAD⁺ biosynthesis via the salvage pathway. This coexists with overexpression of genes involved in recognition of NAD⁺ and fatty acids, a surrounding lipid environment dominated by exogenous oleic acid and an alternatively activated macrophage profile, which culminate in a healthy expansion of WAT and improvement of several hallmarks that typify the metabolic syndrome.

CONCLUSION

Niacin in combination with dietary MUFAs can favor WAT homeostasis in the development of HFD-induced obesity and metabolic syndrome.

Mesenchymal stem cells: Cell therapy and regeneration potential

Rapid advances in the isolation of multipotent progenitor cells, routinely called mesenchymal stromal/stem cells (MSCs), from various human tissues and organs have provided impetus to the field of cell therapy and regenerative medicine. The most widely studied sources of MSCs include bone marrow, adipose, muscle, peripheral blood, umbilical cord, placenta, fetal tissue, and amniotic fluid. According to the standard definition of MSCs, these clonal cells adhere to plastic, express cluster of differentiation (CD) markers such as CD73, CD90, and CD105 markers, and can differentiate into adipogenic, chondrogenic, and osteogenic lineages in vitro. However, isolated MSCs have been reported to vary in their potency and self-renewal potential. As a result, the MSCs used for clinical applications often lead to variable or even conflicting results. The lack of uniform characterization methods both in vitro and in vivo also contributes to this confusion. Therefore, the name "MSCs" itself has been increasingly questioned lately. As the use of MSCs is expanding rapidly, there is an increasing need to understand the potential sources and specific potencies of MSCs. This review discusses and compares the characteristics of MSCs and suggests that the variations in their distinctive features are dependent on the source and method of isolation as well as epigenetic changes during maintenance and growth. We also discuss the potential opportunities and challenges of MSC research with the hope to stimulate their use for therapeutic and regenerative medicine.

Adipose-derived stem cells delay muscle atrophy after peripheral nerve injury in the rodent model

INTRODUCTION

Injuries to peripheral nerves cause distal muscle atrophy. The effects of adipose-derived stem cell (ASC) injections into a muscle after injury were examined.

METHODS

A 1.5 cm defect in the rat sciatic nerve was created, resulting in gastrocnemius muscle atrophy. The nerve defect was repaired with autograft; DiR-labeled ASCs were injected into the gastrocnemius immediately postoperatively. Quantitation of gross musculature and muscle fiber area, cell survival, fibrosis, lipid deposition, inflammation, and reconstructive responses were investigated.

RESULTS

ASCs were identified in the muscle at 6 weeks, where injections showed increased muscle mass percentage retained, larger average fiber area, and less overall lipid content accumulated throughout the musculature. Muscles having received ASCs showed increased presence of interlukin-10 and Ki67, and decreased inducible nitric oxide synthase (iNOS).

DISCUSSION

This investigation is suggestive that an ASC injection into denervated muscle post-operatively is able to delay the onset of atrophy. Muscle Nerve 59:603-603, 2019.

Peptide-modified methacrylated glycol chitosan hydrogels as a cell-viability supporting pro-angiogenic cell delivery platform for human adipose-derived stem/stromal cells

Cell-based therapies involving the injection of adipose-derived stem/stromal cells (ASCs) within rationally designed biomaterials are a promising approach for stimulating angiogenesis. With this focus, the current work explored the effects of incorporating integrin-binding RGD or IKVAV peptides within in situ-gelling N-methacrylate glycol chitosan (MGC) hydrogels on the response of encapsulated human ASCs. Initial studies focused on hydrogel characterization to validate that the MGC, MGC-RGD, and MGC-IKVAV hydrogels had similar biomechanical properties. ASC viability following encapsulation and culture under 2% O2 was significantly impaired in the MGC-IKVAV group relative to the MGC and MGC-RGD groups. In contrast, sustained viability, along with enhanced cell spreading and metabolic activity were observed in the MGC-RGD group. Investigation of angiogenic transcription suggested that the incorporation of the peptide groups did not substantially alter the pro-angiogenic gene expression profile of the encapsulated ASCs after 7 days of culture under 2% O2. Consistent with the in vitro findings, preliminary in vivo characterization following subcutaneous implantation into NOD/SCID mice showed that ASC retention was enhanced in the MGC-RGD hydrogels relative to the MGC-IKVAV group at 14 days. Further, the encapsulated ASCs in the MGC and MGC-RGD groups promoted murine CD31⁺ endothelial cell recruitment to the peri-implant region. Overall, the results indicate that the MGC-RGD and MGC hydrogels are promising platforms for ASC delivery, and suggest that strategies that support long-term ASC viability can augment in vivo angiogenesis through paracrine mechanisms. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 571-585, 2019.

Adipose Stem Cell Translational Applications: From Bench-to-Bedside

During the last five years, there has been a significantly increasing interest in adult adipose stem cells (ASCs) as a suitable tool for translational medicine applications. The abundant and renewable source of ASCs and the relatively simple procedure for cell isolation are only some of the reasons for this success. Here, we document the advances in the biology and in the innovative biotechnological applications of ASCs. We discuss how the multipotential property boosts ASCs toward mesenchymal and non-mesenchymal differentiation cell lineages and how their character is maintained even if they are combined with gene delivery systems and/or biomaterials, both in vitro and in vivo.